Mayor of Buenos Aires prays for gold as archaeologists raise Spanish vessel found while building apartment blockGiles Tremlett guardian.co.uk, Wednesd

Mayor of Buenos Aires prays for gold as archaeologists raise Spanish vessel found while building apartment block.

Archaeologist Marcelo Norman Waissell holds a cannonball near two cannon of a Spanish galleon found while excavating a Buenos Aires building site. Photograph: Marcos Brindicci/REUTERS

Construction workers excavating the foundations of a luxury apartment block overlooking the river Plate in Buenos Aires may have dug up something far more valuable than what they are building.

The workmen uncovered the well-preserved remains of a 17th-century Spanish galleon, one of thousands that carried goods across the Atlantic when Argentina was a Spanish colony.

Eight metres of silt had covered and conserved the galleon in the 300 years since it sank or was abandoned by colonists.

At that time the exclusive Puerto Madero neighbourhood of the Argentinian capital was just a beach on the shores of the Plate. "The galleon was buried under Puerto Madero, in the sedimentation of a beach where many ships used to arrive centuries ago," explained city hall officials.

Five large cannons and a cannonball were among the first objects found by archaeologists who joined the workmen to excavate the site properly.

Speculation that the galleon may be carrying treasure is rife in Buenos Aires, with even the mayor, Mauricio Macri, praying for a find. "I hope there is a great treasure trove on board," he joked. "That way we can pay for many more public works."

So far, however, the only objects dug up apart from the cannons are ropes and old jars of olive oil. The galleon appears to have sunk as it was trying to reach the port at Buenos Aires.

"We feel it must be Spanish because we have not found signs of anything English," one archaeologist, Marcelo Weissel, told La Nación newspaper. "Our hypothesis is that it is from the end of the 17th or the beginning of the 18th century because we have not found any glass recipients which started appearing from Holland around 1720." Carbon dating would eventually give a better idea of when the vessel went down, he said.

Mayor Macri ruled out handing over the galleon's contents to Spain, saying that it belonged to the people of Buenos Aires.

Hernan Lombardi, the head of the city's culture department, said the find was unique and city archeologists planned to raise the whole ship, which would later be opened to the public.

"Now is the time to get down to some careful work," he said.

Development in the Puerto Moreno district began a decade ago. A complex of apartments, shop and offices is due to go up on the site where the galleon was found.